The present invention relates to analytical devices, and more particularly to analytical devices for determining the fusibility of coal and coke ash.
Before coal or coke is burned in a furnace, the fuel should be analyzed to determine the fusibility of the coal or coke ash. Burning coal or coke in a commercial steel mill furnace, which generates temperatures sufficiently high to fuse the ash, causes the ash to collect on various furnace components, most notably the furnace grates. If collection becomes excessive, the furnace must be shut down, cooled, and cleaned, requiring excessive periods of furnace inactivity.
The ASTM standard test method for determining the fusibility of coal and coke ash requires the ash to be formed into triangular pyramid cones which are placed within an analytical furnace. The temperature within the furnace is then ramped at 15.degree. F. per minute, and the cones are manually observed to detect changes in shape. The fusibility of the ash is reported in four temperatures; namely, (1) the temperature at which the apex of the cone becomes rounded, (2) the temperature at which the height of the deformed cone is equal to the width of the base, (3) the temperature at which the height of the deformed cone is equal to one-half the width of the base, and (4) the temperature at which the cone has been reduced to a lump having a height no greater than one-sixteenth inch. This test method has several significant drawbacks. First, the method is time-consuming and requires an observer to constantly monitor all cones within the furnace as all cones pass through all four stages of fusion. This task is boring and the observer can become inattentive, resulting in inaccurate temperature readings. Second, monitoring the shape of five cones (the typical furnace load) is difficult. Third, the empirical findings are somewhat subject to the individual judgment of the human observer, further introducing error and variation into the test rsults. The ASTM test method recognizes these problems and provides for relatively large acceptable error for each of the four stages of fusion in excess of 50.degree. C. or 100.degree. F.
Although at least two known devices have been developed in an attempt to reduce the time-consuming and tedious chore of observing the cones, these devices are not without their drawbacks. One such device is sold as an add-on unit for conventional furnaces and comprises a closed circuit camera and monitor and a video tape recorder coupled thereto. The operator initiates the test and activates the video tape recorder to make a record of the analysis run. After the test is complete, the operator may replay the tape at a relatively rapid speed to determine the fusibility criteria for each cone. However, this equipment and method is still subject to the individual judgment of the operator in evaluating cone shape. Further, reviewing the entire video tape after a test run is just as tedious and boring as watching the test itself.
Another known device is also sold as an add-on unit for conventional furnaces and includes a closed circuit camera and a computer coupled thereto to analyze the video image on the camera. However, as well as in the above-described unit, the vidicon tubes provide poor performance under the high light intensity of the white-hot cones and furnace interior. Second, the vidicon tubes frequently burn out due in part to the high light intensities involved. Third, the computer required to analyze the video image, and the software implementing the analyzing procedure, is relatively complicated since the computer must distinguish and separately analyze each of the individual cones (typically five) within the furnace which are present in the single video image.